Vaso-occlusive devices are surgical implants that are placed within the vasculature of the human body, typically via a catheter, either to block the flow of blood through a vessel making up that portion of the vasculature by formation of an embolus, or to form such an embolus within an aneurysm stemming from the vessel. A common vaso-occlusive device is an embolization coil configured as a helically wound coil that is introduced to a treatment site in the body. For example, the helically wound coil may have a spiral, tornado, or stacked configuration. Spider-like devices are used to contain coils when vessels are large and/or flow is high. Synthetic fibers can be included in the coil to assist with activation of the clotting cascade. Typically, the procedure utilizing the embolization coil includes delivering the coil portion of the device to the treatment site via catheter, wherein the coil separates from the device and remains in the body, forming the desired obstruction. The pusher wire and catheter are then retrieved from the body.
Another example of a vaso-occlusive device is an expandable occluding device 310 comprising an outer metal fabric surrounding an inner metal fabric, each comprising a plurality of braided metal strands 312, an example of which is shown in FIGS. 1a-b. The expandable occluding device 310 has proximal and distal ends 314, 316, each incorporating clamps 318 for securing the plurality of braided strands 312 that comprise the inner and outer metal fabrics together. The expandable occluding device 310 is shaped to create an occlusion of an abnormal opening in a vascular organ when in its expanded preset configuration, as illustrated in FIG. 1b. The expanded preset configuration is deformable to a lesser cross-section dimension for delivery through a channel in a patient's body, as illustrated in FIG. 1a. Both the outer and inner metal fabrics have a memory property such that the medical device tends to return to the expanded preset configuration when unconstrained. Accordingly, the expandable occluding device 310 remains in the expanded configuration which permits it to maintain a constant radially outward force in the direction of arrows 320 at the treatment site within the body vessel 322.
While occluding devices such as the previously described vaso-occlusive devices provide a number of advantages, they serve to hold the vessel open during embolization. Therefore, it is the material used for embolization that is important in effectively occluding blood flow and it is important to hold the material in place within the vessel. When vessels are large and/or flow is high, such devices may not be as effective. Thus, there exists a need for an improved occluding device.